The poison billowed over the garden hedge, smothering the young girl with a fine dusting of toxins. That night Georgina Downs's mouth erupted in blisters and her throat bled. She became chronically weak, so frail that for days she could barely sit upright.

But it was just the beginning of an ordeal which would blight her childhood, ruin her parents' health and lead her to uncover a scandal which may explain cases of cancer, brain disease and mystery conditions throughout rural Britain.

She believes that her family's health has been destroyed by persistent exposure to chemicals through the widespread practice of spraying crops - and, inadvertently, nearby gardens - with massive amounts of pesticide.

Her plight has prompted Georgina, now 29, to launch a one-woman campaign which has exposed an astonishing failure by the Government to protect the public's health or even to investigate the risks of pesticides.

Exhaustive inquiries by Georgina have uncovered scores of similar cases, galvanising such support that the campaign could result in a multi-million-pound compensation claim from victims if Ministers fail to respond to their concerns.

Many are confident they could sue ministers for presiding over a regulatory framework that has allowed families to be poisoned on their own property.

'Running, organising and co-ordinating this quest for justice has been my life for two years,' Georgina said. 'I had to give up my job. It's gone too far to give up now. The law has to change.'

Her fight has been far from easy. Only a combination of meticulous planning and sheer audacity have ensured her voice has been heard. Her tactics included staying at hotels where she knew relevant government scientists were staying so she could harangue them in the lobby, and confronting ministers at conferences.

Georgina has forced ministers to concede that crop-spraying needs to be re-examined. Action has been promised later this year.

The move is a first major triumph for Georgina who, for nine years, played on the lawn of her Sussex home yards from where a farmer spewed a cocktail of pesticides into the air. Eventually her body could take no more. At 18 it had reached toxic overload. She was admitted to hospital with chronic muscle wastage. Her father Ray's eyeballs were later burned - his eyesight forever affected - after being caught in a chemical spray. Jeanne, her mother, suffers intense fatigue and weakness.

Two years ago Georgina began to investigate what could have happened to their family and discovered the farmer was legally permitted to hurl poisonous chemicals into the air on the edge of their home. No adequate risk assessment to humans nearby had been carried out, nor had the cumulative effects that chemicals designed to kill organisms might have on local residents been sufficiently examined.

Even more disturbingly, she discovered ministers had been repeatedly warned of the toxic capacity of pesticides for more than 50 years. A 1951 paper by senior scientists demanded tough powers to limit pesticide use.

Her investigations have uncovered a network of clusters of unexplained illnesses in communities surrounded by farmland doused with pesticides. In one village, one resident has counted 38 cases of serious illness, whose symptoms have all been linked to pesticide poisoning.

A hamlet in East Anglia appears to have been drenched in chemicals. In the 12 houses in the community, doctors have recorded a horrifying tally of symptoms. Parkinson's disease, multiple sclerosis, labrynthitis, convulsions, epilepsy, sleeplessness, miscarriages, asthma, depression and acute allergic reactions have all been reported. The cancer victims include the death of a young child whose mother was subjected to crop spray exposure while pregnant.

'Spray operators dress in protective clothing to protect them from the effects of the chemicals. But what about the people who live in the area?' said one resident.

Despite requests from the villagers to investigate the complaints, no action has been taken.

Disquiet is also mounting among residents of a Worcestershire village who told the Observer of a similar litany of suffering.

From just 50 properties, one resident has recorded four cases of leukaemia, including his son who died from the illness in his 30s, seven cases of cancer and six neurological diseases. In addition several dogs which walked through fields shortly after crop spraying have died from cancer. Entire ponds of fish have also died following spraying.

More than 250,000 people live next to intensively sprayed farms, creating the potential for a vast number of victims.

Anger is mounting that Ministers have neglected to safeguard the public who - unlike the crop sprayers - are not wrapped in protective clothing when pesticides are injected into the atmosphere.

When Georgina's determination ensured she could present her evidence to ministers after months of campaigning, she discovered that deep misgivings over pesticide use existed in Whitehall.

Yet it was hardly surprising. Seven years ago Meacher produced a paper warning of the potential dangers of organophosphates. It revealed that of hundreds of incidents, three-quarters involved the public and 60% involved pesticide spraying.

Studies seen by ministers also reveal that pesticides have been found as far as three miles away from fields.

More than 25,000 tonnes of pesticides are coated on the UK countryside every year. Safety agencies have no idea where these drops settle. The official method for assessing the risks to human health is based on the 'bystander' principle, which assumes that people are subjected to occasional short-term exposure.

Testing long-term exposure - such as someone living next to a treated field - have never been made in the UK.

In the next few months ministers are expected to make a decision on whether a 'buffer zone' needs to be introduced between crop-sprayed fields and homes.

A spokesman for the Department of Environment, Food and Rural Affairs said: 'Independent scientific advice is that no actions needs to be taken on safety grounds.'

He added that if farmers obeyed the industry's 'green code' there would be no problem.

Such advice contradicts the behaviour of inspectors from the Health and Safety Executive, which has a statutory duty to protect public health. One even refused to stand in Georgina's garden during spraying, citing health grounds. She said another admitted, after being caught in a spray of agricultural organophosphorous pesti cides, that it had burned his car's paintwork.Yet until the Government acts, the Downs family will be forced to spend their days trapped indoors.

The fields next door to the Downs are to be planted with lettuce - one of the most intensely pesticide-sprayed crops in the UK. All they want is a breath of fresh air.